The Justice Department released documents today detailing how officials prepared a Feb. 4 letter to Sen. Chuck Grassley (R-Iowa) that Attorney General Eric Holder has since admitted contained false information about Operation Fast and Furious, a botched gun operation under investigation by Congress.

The documents show that Dennis Burke, then a U.S. attorney who has since resigned, and William Hoover, then the deputy director of the Bureau of Alcohol, Tobacco, Firearms and Explosives who has since been reassigned, principally provided the false information to officials who drafted the letter. But the documents do not shed light on whether either knew the information was false at the time.

In the Feb. 4 letter, Assistant Attorney General Ronald Weich broadly denied that ATF officials had allowed assault weapons to “walk,” which meant ending surveillance on weapons suspected to be en route to Mexican drug cartels, allowing the guns to escape into the wild. “ATF makes every effort to interdict weapons that have been purchased illegally and prevent their transportation to Mexico,” Weich wrote.

Grassley’s allegations about Fast and Furious, later revealed to be true, “are based on categorical falsehoods,” Burke wrote in a Jan. 31 email. Faith Burton, a Justice Department official who drafted an early version of the letter, took notes based on a phone conversation with Hoover that read, “ATF doesn’t let guns walk.”

Emails show Lanny Breuer, the assistant attorney general for the department’s criminal division, received versions of the letter on four occasions via email. Breuer forwarded the emails to a personal account but told Congressional investigators in a written statement today he “cannot say for sure” whether he viewed the drafts.

Breuer conceded Oct. 31 he knew federal officials allowed assault guns and other weapons to fall into the possession of Mexican drug cartels as early as April 2010, 10 months before the department denied in the letter to Grassley that the investigative strategy was used.

“Any instance of so-called gunwalking was unacceptable. This tactic was unfortunately used as part of Fast and Furious,” Holder admitted to Senators at a Judiciary Committee hearing Nov. 8. “This should never have happened.”

Breuer’s knowledge of the tactic was about Operation Wide Receiver, a similar, smaller-scale weapons-smuggling investigation that began during President George W. Bush’s administration.

Breuer said in October it was a “mistake” not to alert higher-ranking officials when the information about gunwalking in Fast and Furious “became public,” given his knowledge about Wide Receiver.

The documents released today show tangential involvement by Breuer in preparing the Feb. 4 letter.

“Let me know what’s happening with this,” he wrote in a Feb. 1 email asking for an update.

Jason Weinstein, Breuer’s deputy, responded by saying he had revised the initial draft, written by Burton, to “make it a little tougher.”

The documents show Weinstein was intimately involved in drafting the letter, urging repeated changes to strengthen the tone of its denial over objections from the Office of Legislative Affairs headed by Weich.

Weinstein was also far more familiar than Breuer with the details of Operation Wide Receiver, according to documents released in October. For instance, Weinstein told colleagues in an April 12, 2010, email that the ATF should be “embarrassed that they let this many guns walk” in Wide Receiver.

According to Breuer, Weinstein is now also expressing regret about not connecting the dots between Wide Receiver and Fast and Furious.

“Weinstein has expressed to me that, in hindsight, he wishes he had not relied on those assertions and that, because he did rely so heavily on them, he viewed, incorrectly, the misguided tactics used in Operation Wide Receiver — which resulted in the ATF losing control of guns that then crossed the border into Mexico — as having no relation to the allegations that were being made about Operation Fast and Furious,” Breuer said today in a written statement to Congressional investigators.

The day before the letter was sent to Grassley, the Office of the Deputy Attorney General raised concerns about the scope of the denial it contained.

“In the 2nd full para[graph] — we say ‘categorically false’ — obviously we want to be 300% sure we can make such a ‘categorical’ statement,” Lisa Monaco wrote in an email after reviewing a draft version of the letter. “I’ve developed an aversion to adjectives and oversight letters,” she explained in a later email.

The language was ultimately removed.

Over the course of the letter being prepared, Burke vehemently argued the department should more vigorously deny the allegations.

“What is so offensive about this whole project is that Grassley’s staff, acting as willing stooges for the Gun Lobby, have attempted to distract from the incredible success in dismantling [southwest border] gun trafficking operations ... but, instead, lobbing this reckless despicable accusation that ATF is complicit in the murder of a fellow federal law enforcement officer,” he wrote in a Feb. 4 email.

“Well said Dennis. Thank you!” Hoover replied.

However, guns found at the scene of Border Patrol Agent Brian Terry’s murder were eventually connected to the Fast and Furious operation.

A spokeswoman for Grassley said, "After a first glance at today's document dump from the Justice Department, there appears to be even more questions for Assistant Attorney General Breuer, Deputy Assistant Attorney General Weinstein and former U.S. Attorney Dennis Burke."